Microbiology

1. Haemophilus
Buga Rudolf
HTC LECTURE SERIES

2. Introduction
Family Pasteurallaceae (Pasteurella and
Actinobacillus)
Also known as Parvobacteria
Species: H.influenzae, H.parainfluenzae,
H.ducreyi, H.aegptius,
H.haemolyticus,H.parahaemolyticus,
H.segnis, H.aphrophilus and
H.paraphraphrophilus.
H.influenzae the commonest of medical
importance.

3. Introduction…
Haemophilus – ‘’ haem lover’’
Require complex media and growth factors for growth.
Growth factors: X factor (haematin) and V factor ( NAD
and NADP/Co-enzyme I and II)
Best growth on Choc agar than BA
Growth atm:Opt TO 35 – 370 C; pH – 7.6 and ambient
air plus 5-10 % CO2
Glycolytic and respiratory growths using nitrate as final
electron acceptor is possible

4. H. influenzae
Microscopy:
Gm positive cocco-bacilli
Encapsulated strains (CSF), coccobacilli, 0.2-0.3µm
by 0.5 – 0.8µm.
Non-encapsulated strains (sputum) are pleomorphic
and at times filamentous
Appears gram negative if not properly Gram stained
Some elongated forms (sputum) may show bipolar
staining, leading to erroneous diagnosis as
Streptococcus pneumoniae

5. Habitat
Adapted to human hosts
Occur in the nasopharynx of about 75% of
healthy children and adults
Non encapsulated forms normally occur as
normal flora
Intermittent occurrence of encapsulated Hib is
found in the URT of 3-7% of healthy people
Pharyngeal carriage is important in the
transmission of Hib.

6. Diagnosis
1. Direct detection: Capsular Ags in CSF
2. Culture:
Sputum and CSF culture on Choc and BA,
done promptly since the organisms are fragile
Colonies are small on BA than Choc (24-
48hrs)
Incubation atmosphere: O2 + 5-10% CO2
Blood culture positive in meningitis

7. Diagnosis…
3. Identification:
•Gram stain
•Sateletism
•X and V factors

8. Pathogenesis
Hib colonizes the nasopharynx
Penetrate the epithelium and capillary
endothelium to cause bacteremia
Meningitis result from direct spread via
lymphatic drainage or from haematogeneous
spread
Capsules resist phagocytosis and complement
mediated lysis in non immune host
Non encapsulated strains are less invasive but
can induce inflammatory response that can cause
disease
Outbreaks of Hib may occur in nurseries and
childcare centers

9. Virulence factors
•Lipopolysaccharides (LPS)
•Neuraminidase
•IgA protease
•Fimbriae

10. Host defenses
•Serum antibodies to
oCapsular antigens (Hib) or
oSomatic antigens
•Abs are bactericidal and promote
phagocytosis

11. Diseases caused
Hib: meningitis, epiglottitis, bacteremia,
cellulitis, osteomyelitis, septic arthritis,
pericarditis or endocarditis
Non typable Hin: Otitis media, sinusitis,
tracheobronchitis and pneumonia
Other species: H. parainfluenzae-
pneumonia and endocarditis; H. ducreyi-
chancroid; H. aegyptius- conjunctivitis

12. Epidemiology
Hib is widely spread in human population
First isolated by Pfeiffer during the influenza
pandemic of 1890
Hin colonizes healthy children and adults
but the rate is more for non typable strains
Spread is by direct contact, secretions and
aerosols
NB: H.ducreyi is spread by venereal contact
No animal reservoirs for these organisms

13. Antibiotics/Control
•Ampicillin (for non beta-lactamase
producers)
•3rd Generation Cephalosporins
(Cefotaxime, Ceftriaxone, Ceftazidime),
Chloramphenicol,
Amoxycillin/Clavulanic acid,
Tetracycline
•Hib –vaccine